Multi-level disk drive motor speed control

Abstract

A three level motor speed control for a device such as a magnetic disk drive requiring a closely regulated running speed provides for acceleration, deceleration, obtaining close speed regulation and maintaining speed regulation of a rotating device during operation. The first level control provides acceleration or deceleration while checking velocity each eighth revolution and the second level control uses single revolutions to measure speed over an accurate rotational distance to obtain close speed regulation. Both level one and level two are controlled by the device controller. During run conditions with no error signal, a third level of control of the closely regulated velocity is maintained by separate hardware circuits which frees the processor for other uses. An error condition forces control to level one for re-establishment of the regulated running speed and a command to stop the drive forces control to level one for deceleration and stop procedures.

What is claimed is: 
     
       1. In an information storage device including a rotating information carrying media, a motor for driving the rotating media and a processor unit, a motor drive control for regulating the rotational speed of the rotating media comprising: first means for accelerating said information carrying media to an operating speed and effecting rotational speed regulation within a predetermined range under control of said processor unit;   digital circuit means for maintaining said information carrying media speed within a predetermined range of rotational velocities, whereby said processor unit is freed to handle non-motor related matters during no error operation; and   sensing means for transferring motor drive control to said first means when an error condition occurs with respect to speed regulation effected by said digital circuit means.   
     
     
       2. In an information storage device wherein data is stored on a rotating media on concentric tracks divided into sectors, each of which has a prerecorded pattern, including a rotating information carrying media, a motor for driving the media and a processor unit, a motor drive control for regulating the speed of said rotating media connected to said motor comprising: first means for accelerating said information carrying media to an operating speed and effecting rotational speed regulation within a predetermined range under control of said processor unit;   digital circuit means including counter means for generating a count between consecutive sector patterns for maintaining said rotating information carrying media speed within a predetermined range of rotational velocities, whereby said processor unit is freed to handle non-motor related matters during no error operation;   decode means responsive to the count generated between sector patterns; and   output means that is actuated when said decode means determines that the rotational velocity of said rotating media is less than a predetermined value during the passage of the sector represented by said count.   
     
     
       3. The information storage device of claim 2 wherein said first means includes a first level wherein speed is measured by counting means within said processor unit a plurality of times during each revolution of said rotating media until a predetermined speed is attained; and   a second level wherein rotational speed is determined by sensing rotation of said rotating media once per revolution until a predetermined range of speed regulation is achieved and   further comprising switching means for transferring control of said motor from said first means to said digital circuit means when said predetermined range of speed regulation is achieved by said second level.   
     
     
       4. The information storage device of claim 3 further comprising error sensing means associated with said processor unit for sensing an error condition related to the rotating media speed regulation effected by said digital circuit means and for transferring control of said motor to said first means first level when an error condition is sensed.   
     
     
       5. The information storage device of claim 3 wherein said first means second level includes speed regulation means comprising a first motor duty cycle and a second motor duty cycle of longer duration than said first motor duty cycle and   selection means for selecting said first motor duty cycle when the rotational velocity of said rotating media during one rotation exceeds a predetermined value and for selecting said second duty cycle when the rotational velocity of said rotating media during one revolution does not exceed said predetermined value.   
     
     
       6. The information storage device of claim 5 wherein said second motor duty cycle is at least twice the duration of said first motor duty cycle.